Catch organism assemblages along artificial reefs area and adjacent waters in Haizhou Bay

To better understand the community patterns mediated by connectivity in artificial reefs of coastal areas, it is necessary to understand the distribution and coexistence of organisms with artificial reefs area and adjacent waters. This study was conducted to examine main catches assemblages collected by trawls in Haizhou Bay,which included five habitats: the artificial reef area(AR), aquaculture area(AA), natural area(NA), estuary area(EA) and comprehensive effect area(CEA). The result shows that the total abundances of species in the five habitats were highly different(univariate PERMANOVA: P = 0.001, n = 24), but some species were also unique in their habitat(e.g. Scapharca subcrenata and Glossaulax didyma in AA). The body size distribution of specific species between habitats are different. For Collichthys lucidus, their body size in AR(14.63 cm ± 1.64 cm) and EA(14.3 cm ± 0.85 cm) is higher than that in NA(10.65 cm ± 1.64 cm), CEA(11.28 cm ± 1.85 cm) and AA(12.1 cm ±0.43 cm), which indicates the potential connection from AR to EA mediated by their adult population. We concluded that artificial reefs in AR can be considered key components that have the ability to support species assemblages in adjacent habitats. This study has implications for the conservation and monitoring of species assemblages in coastal areas in terms of that artificial reefs can be applied in different stages of habitat protection implementation and in different combinations of scenarios.

The Variation of Plankton Community Structure in Artificial Reef Area and Adjacent Waters in Haizhou Bay

Plankton are an important component of marine protected areas(MPAs),and its communities would require much smaller interpatch distances to ensure connection among MPAs.According to the survey from MPAs dominated by artificial reefs and adjacent waters(estuary area(EA),aquaculture area(AA),artificial reef area(ARA),natural area(NA)and comprehensive effect area(CEA))in Haizhou Bay in spring and autumn,we analyzed phyto-zooplankton composition,abundance and biomass,and correlation with hydrologic variables to gain information about the forces that structure the plankton.The results showed that the dominant zooplankton were copepods(spring,98.9%;autumn,94.2%),while the phytoplankton were mainly composed of Bacillariophyta(spring,61.8%;autumn,95.6%).The RDA results showed that temperature,salinity and depth highly associated with the distribution and composition of plankton species among the habitats than other factors in spring;temperature,Chla and DO had the strongest influence in autumn.The zooplankton in the ARA and AA ecosystems basically contained the same species as those in other habitats,and each habitat also exhibited a relatively unique combination of plankton species.The structures of the EA zooplankton in spring and the EA phytoplankton in both seasons were much different than other habitats,which may have been caused by factors such as currents and tides.We concluded that there exists similarity of the plankton community between artificial reef area and adjacent waters,whereas the EAs may be relatively independent systems.Therefore,these interaction between plankton community should be considered when designing MPA networks,and ocean circulations should be considered more than the environmental factors.

Flow Field Characteristics of Multi-Trophic Artificial Reef Based on Computation Fluid Dynamics

On the basis of computational fluid dynamics,the flow field characteristics of multi-trophic artificial reefs,including the flow field distribution features of a single reef under three different velocities and the effect of spacing between reefs on flow scale and the flow state,were analyzed.Results indicate upwelling,slow flow,and eddy around a single reef.Maximum velocity,height,and volume of upwelling in front of a single reef were positively correlated with inflow velocity.The length and volume of slow flow increased with the increase in inflow velocity.Eddies were present both inside and backward,and vorticity was positively correlated with inflow velocity.Space between reefs had a minor influence on the maximum velocity and height of upwelling.With the increase in space from 0.5 L to 1.5 L(L is the reef lehgth),the length of slow flow in the front and back of the combined reefs increased slightly.When the space was 2.0 L,the length of the slow flow decreased.In four different spaces,eddies were present inside and at the back of each reef.The maximum vorticity was negatively correlated with space from 0.5 L to 1.5 L,but under 2.0 L space,the maximum vorticity was close to the vorticity of a single reef under the same inflow velocity.

Studies on Factors Influencing Hydrodynamic Characteristics of Plates Used in Artificial Reefs

As a simplified model of artificial reefs, a series of plate models punched with square or circular openings are designed to investigate the effects of openings on the hydrodynamic characteristics of artificial reefs. The models are grouped by various opening numbers and opening-area ratios. They are physically tested in a water flume or used in the numerical simulation to obtain the drag force in the uniform flow with different speeds. The simulation results are found in good agreement with the experimental measurements. By the non-dimensional analysis, the drag coefficient specified to each model is achieved and the effects of openings are examined. It is found that the key factor affecting the drag coefficient is the open-area ratio. Generally, the drag coefficient is a linear function of the open area ratio with a minus slope. The empirical formulae for the square and circular openings respectively are deduced by means of the multiple regression analysis based on the measured and numerical data. They will be good references for the design of new artificial reefs. As a result of numerical simulation, the vorticity contours and pressure distribution are also presented in this work to better understand the hydrodynamic characteristics of different models.

Distribution Characteristics of Fat Greenling(Hexagrammos otakii) Inhabiting Artificial Reefs Around Qiansandao Island, Haizhou Bay, China

Chinese government has provided vigorous financial supports to artificial reef(AR)projects to repair marine ecosystem.Qiansandao AR,an important AR project of Fishery Resource Restoration Program in Shandong Province,was built during 2002 to 2007.It has enhanced the local fishery harvest and generated positive economic benefits.Fat greenling(Hexagrammos otakii)is a major commercial reef fish in Qiansandao with high economic values.Its distribution characteristics need to be further studied.In this research,we studied the potential influence of environmental variables and distance from ARs on catch per unit effort(CPUE)and body length of fat greenlings.The results showed that the average body length of fat greenlings distributed within 10 m from ARs was longer than that of fat greenlings distributed more than 600 m away from ARs.Body length also increased with the increased salinity,while it declined as temperature increased.The probability of the presence of fat greenling increased when temperature was below 20℃,then it slightly decreased.CPUE decreased as the distance increased.Our results elucidate the potential effects of environmental variables and distance from ARs on the distribution of fat greenling,which may also be helpful to the distribution research of other reef fish species.

Community structure of planktonic copepods in artificial reefs of Wenchang,Hainan

To understand the characteristics of population structure of planktonic copepods and their response mechanisms to marine environmental factors in different seasons,the community structure of planktonic copepods in samples obtained from 7 stations in artificial reefs of Wenchang,Hainan Province in March and September 2019 were investigated.A total of 33 species of planktonic copepods belonging to 23 genera within 17 families were identified in artificial reefs,with 27 species and 21 genera in spring,and 23 species and 19 genera in fall,respectively.The identified planktonic copepods were further categorized into estuarine groups,warm temperate groups,warm water coastal groups,and warm water widespread groups.The predominant species in spring were mainly composed of Temora turbinata and Canthocalanus pauper,whereas Tortanus gracilis and Subeucalanus subcrassus were dominant species in fall.The species and abundance of planktonic copepods in spring were higher than that in fall,while the diversity index and evenness were vice versa,with obvious seasonal differences.In addition,there was a correlation between the population of copepods and physicochemical environmental factors.The major warm water group of copepods in spring showed different degree of correlation with environmental factors,such as NO2-N,NH3-N,pH,water depth,temperature etc.,while the population of copepods in fall was affected by limiting factors such as dissolved oxygen,pH,and temperature.In conclusion,copepods species inartificial reefs were rich and diverse,and their community structure tended to be stable.In addition,the surrounding water quality was generally good,and the whole marine ecosystem and ecological environment were in good condition.

Succession and seasonal variation in epilithic biofilms on artificial reefs in culture waters of the sea cucumber Apostichopus japonicus

Periphytic biofilms in aquaculture waters are thought to improve water quality, provide an additional food source, and improve the survival and growth of some reared animals. In the AsiaPacific region, particularly in China, artificial reefs are commonly used in the commercial farming of sea cucumbers. However, few studies have examined the epilithic biofilms on the artificial reefs. To gain a better understanding of the succession of epilithic biofilms and their ecological processes in sea cucumber culture waters, two experiments were conducted in culture waters of the sea cucumber Apostichopus japonicus in Rongcheng, China, using artificial test panels. On the test panels of succession experiment, more than 67 species were identified in the biofilms. On the test panels of seasonal variation experiment, more than 46 species were recorded in the biofilms. In both experiments, communities of epilithic biofilms were dominated by diatoms, green algae and the annelid Spirorbis sp. In the initial colonization, the dominant diatoms were Cocconeis sp., Amphora spp. and Nitzschia closterium in June, which were succeeded by species of Navicula, Cocconeis and Nitzschia(July to September), and then by Licmophora abbreviata, Nitzschia closterium and Synedra spp. in the following months. A diatom bloom in the autumn and filamentous green algae burst in the summer were also observed. Ecological indices well annotated the succession and seasonal changes in epilithic communities. Multidimensional scaling(MDS) analysis found significant differences in diatom community composition among months and seasons. Fast growth of biofilms was observed in the summer and autumn, whereas the biomass of summer biofilms was largely made up of filamentous green algae. Present results show that the components of epilithic biofilms are mostly optimal foods of A. japonicus, suggesting that biofilms on artificial reefs may contribute important nutritional sources for sea cucumbers during their growth seasons. Future works should include quantitative determination of the contribution of epilithic biofilms to the diet of A. japonicus, potential roles of epilithic biofilms in regulating the water quality of sea cucumber ponds, and the regulation of epilithic biofilms in sea cucumber culture ponds.

Experimental Investigation of Local Scour Around Artificial Reefs in Steady Currents

Artificial reef is a man-made object that is deployed purposefully on the seafloor to restore the offshore fishery resources and the ecological environment.To secure its ecological effects,it is important to study the possible instability of artificial reefs,like drifting and reversing caused by burial and scour in different seafloor conditions.In the present study,experiments of local scour around an artificial reef are carried out in steady currents.The effect of the open-area ratios and the open-hole heights of the cubic reefs,and the bottom angles of the triangular reefs on the time-scale of the scour process and the equilibrium scour depth are investigated.The results indicate that for the cubic artificial reef,the scour depth decreases with the increasing open-area ratios,and increases with the increasing open-hole heights.In the present study,the optimal prototype of the cubic reef with an open-area ratio of 0.49 and open-height of 0.7 m produces the minimum scour depth.For the triangular reef,the scour depth increases when the bottom angle increases.Moreover,based on the experimental results,empirical equations of the effects of the cut-opening and the bottom angle on the maximum equilibrium scour depth are proposed.The formulas will provide theoretical support and practical guidance for the optimized design and construction of artificial reefs.

Research on the rationality of artificial reef layout of Dashentang

By the means of technology of CFD （Computational Fluid Dynamics）, this research has studied the surrounding flow field effect of different combination of artificial reefs. In the study, four kinds of configurations are used to simulate numerically and these are ＂444＂ three columns, ＂464＂ three columns, ＂12345＂ five triangles and the ＂34543＂ five column regular hexagon .The result shows that the combination of artificial reefs of Dashentang can play a good role in regulating the reefs.

Effects of an artificial reef system on demersal nekton assemblages in Xiangshan Bay, China

In 2012,an artificial reef system was deployed in Xiangshan Bay,China,to enhance its fishery resources. To determine the effect of the artificial reef system on the demersal nekton assemblages,a beforeafter-control-impact study design was applied. Comparisons of assemblages from impact and control habitats revealed that the assemblage in the impact area had a gradual response to reef deployment. The assemblages in the impact and control areas changed in different ways after reef deployment. During the study period,total biomass,species richness and average body weight in the control area remained relatively stable,whereas there were significant increases in these indicators in the impact area. Responses to the reefs differed among nekton species,inducing assemblage succession in the reefs post-deployment. Sparus macrocephalus and Cynoglossus abbreviat us benefited most from reef deployment. Conversely,smallsized shrimp Palaemon gravieri showed a progressive decrease in biomass following reef deployment. Overall,the artificial reef system diversified the demersal nekton assemblage,enhanced the total biomass,and increased the proportion of large-sized species.

Particle image velocimetry and numerical simulations of the hydrodynamic characteristics of an artificial reef

This article reports a particle image velocimetry study and the comparative results of a numerical simulation into the hydrodynamic characteristics around an artificial reef.We reveal the process of flow separation and vortex evolution,and compare the force terms generated by our artificial reef model.The numerical simulation agrees well with experimental results,showing the applicability of computational fluid dynamics to the hydrodynamics of an artificial reef.Furthermore,we numerically simulate the hydrodynamics of the reef model for seven velocities.The results show that the drag coefficient is approximately 1.21 in a self-modeling region for Reynolds numbers between 2.123×104and 9×104.Therefore,the upwelling height and current width of the flow field do not change significantly when the inflow velocity increases.Our study indicates that computational fluid dynamics can be applied to study the hydrodynamics of an artificial reef and offer clues to its construction.

Preliminary Evaluation on Resources Enhancement of Artificial Reef in the East Corner of Zhelang Shanwei

In order to analyze the improvement of fish resource,the trawl net and gill net were used in the background survey and investigation in the artificial reef area and control area of the east of corner was discussed in Zhelang Shanwei in January 2003 and April 2010 respectively.Margalef species richness index,Shannon-Winener diversity index and Pileou uniformity index were chosen to analyze the multiformity of biological population and community structure.Resource density index of trawl net investigation and catch rate of gill net were chosen to estimate the variance of biomass.The results of the trawl net showed that the resources density of the artificial area increased by 3.078 times,and numbers of species increased by 1.875 times,squilla being the dominant group instead of the fish,and the first dominant species being squilla oratoria(Oratosquilla oratoria),which increased by 4.372 times before the artificial reef dropped.The results of the gill net showed that the catch rate of the artificial area increased by 12.043 times,numbers of species increased by 1.333 times,the dominant group was fish,it increased greatly,the first dominant species was golden small fish(Sardinella aurita),which increased by 13.035 times before the artificial reef dropped.Both the results of trawl net and gill net indicated that the effect of fish assemblage were evident,and the community structure had improved greatly.It showed a wonderful effect on conservation and assemblage of fishes resource.The artificial reefs developed a new resource enhancement system in the east corner of Zhelang Shanwei accomplished basically.

Relationships Between Community Structure and Environmental Factors in Xixiakou Artificial Reef Area

The construction of artificial reefs has unparallelly developed for a few decades in China.Artificial reefs can be used to manage and conserve commercially exploited fish and crustacea.However,their suitability as ecological niche is poorly characterized.Therefore,in this study,we detected the seasonal variation of community biodiversity and the corresponding driving environmental factors.We also explored the relationships between dominant species and environmental factors to identify appropriate ecological niche areas.Different statistical analysis methods were used to assess species distribution within an artificial reef area in Xixiakou during nine sampling events in four seasons between 2017 and 2018.Non-metric multidimensional scaling(NMDS)and cluster analysis results indicated that the components of community can be divided into two clusters.Complexity of community,which is exhibited by species number,biodiversity,and catch per unit effort(CPUE),was significantly higher in summer than in other seasons.Generalized additive model(GAMs)results revealed the significant effects of temperature and chlorophyll a on the community structure.Sebastes schlegelii,Hexagrammos otakii,Conger myriaster and Charybdis japonica were the dominant species in four seasons.GAMs results indicated that temperature,dissolved oxygen(DO),pH and chlorophyll a affect the CPUE of dominant species significantly.The distinct suitable ecological niche for each dominant species was found in this study.For example,Charybdis japonica preferred to live in the area with 20.7–22.1℃,dissolved oxygen 7.07–7.15 mg L−1 and salinity 31.8–31.9.The results of this study are beneficial to resource conservation and fishery management.

The characteristic of phytoplankton community and its variation at artificial reef area of the coastal sea of Tianjin

Three cruises were investigated respectively in May,July and November 2016 in the artificial reef area of 2010,2012,and 2014 and the non-artificial reef area(control area)in the coastal area of Tianjin.Each area had 3 sampling stations,a total of 12 sites.The result showed that 58 taxa of phytoplankton were identified which belongs to 2 phyla 28 genera,Among these species,bacillariophyta including 19 genera 44 species,pyrrhophyta including 9 genera and 14 species.Give priority to with diatom species,accounting for 75.9%of the total species,followed by dinoflagellates,accounting for 24.1%.Dominant phytoplankton species give priority to with coscinodiscus and Chaetoceros of bacillariophyta,mainly including Coscinodiscus wailesii,C.asteromphalus,C.granii,C.oculus-iridis,C.spp.,Chaetoceros castracanei,C.lorenzianus,C.curvisetus,Pseudo-nitzschiapungens,Guianardia delicatula,Rhizosolenia setigera,Proboscia alata f.indica and Noctilluca scintillans.Phytoplankton cell abundance revealed obviously seasonal changes,the average cell abundance respectively was 94.79×10^4 cells/m^4、39.53×10^4 cells/m^4 and 21.5×10^4 cells/m^3.Phytoplankton diversity index has obviously seasonal variation,and in November,shannon-wiener diversity index,Margalef index and Pielou index are higher than in May and July.Comparing the artificial reef areas with the control area,the phytoplankton cells abundance of the control area in May was significantly higher than the artificial reef areas.In July and November,the artificial reef area of 2014 phytoplankton cell abundance was significantly higher than other artificial reef area and the control area.Diversity index of phytoplankton in the control area and the artificial reef of 2012 was lower than the artificial reef area of 2010 and 2014,and lowest in non-artificial reef areas.Obviously,the construction of artificial reef had significant effect for the improvement of the phytoplankton community diversity,but the phytoplankton community diversity is not always increasing and fluctuating to a certain extent as time goes by.

Research Advances in Hydrodynamics of Artificial Reef

With further recession and deterioration of offshore fishery resources and increasing living demands, construction of marine ranching becomes a focal point to improve marine biological resources and environment, while artificial reef is one of the important parts for marine ranching construction. The artificial reef technology develops slowly in China compared with developed countries, such as the United States and Japan, and there are still many issues urgently to be solved. When an artificial reef is released in water, there are various kinds of forces, and its forces and flow field-effect are closely related to surrounding conditions and its own performance. Currently, there are no mature conclusions on research of hydrodynamics of artificial reef. According to review of hydrodynamics of artificial reefs, we hope to give a full understanding on hydrodynamics performance of artificial reefs, and provide reference and theoretical basis for further research on design and structure of artificial reef in China.

Effects of an artificial oyster shell reef on macrobenthic communities in Rongcheng Bay, East China

An artifi cial oyster shell reef was deployed in Rongcheng Bay, East China. However, the effects of this reef on the surrounding macrobenthic communities were unknown. We compared sedimentary factors, macrobenthic biomass, abundance, and community composition and ecological indicators between the reef and non-reef areas over a one year period. The mean values for chlorophyll a(Chl a), total organic matter(TOM), total organic carbon(TOC), and total nitrogen(TN) content in surface sediments in the reef area were slightly higher than those in the non-reef area. The Chl a levels differed signifi cantly between the two areas, but the TOM, TOC, and TN were not signifi cantly different. The abundance of crustaceans was signifi cantly different between the two areas, but the abundance and biomass of polychaetes, echinoderms, mollusk did not differ signifi cantly. The permutational multivariate analysis of variance(PERMANOVA) revealed that the macrobenthic community differed signifi cantly through time and analysis of similarity multivariate analyses(ANOSIM) revealed that the macrobenthic community differed signifi cantly in some months. The ecological indicators revealed that the environmental quality of the reef area was slightly better than that of the non-reef area. Overall, our results suggest that the artifi cial oyster shell reef may change the macrobenthic community and the quality of the environment. Despite the lack of an effect in the short term, long-term monitoring is still needed to evaluate the effects of artifi cial oyster shell reefs on macrobenthic communities.

Effect of an escape vent in accordion-shaped traps on the catch and size of Asian paddle crabs Charybdis japonica in an artificial reef area

Accordion-shaped traps are widely used in China to catch the Asian paddle crab C harybdis japonica but traps of conventional design often catch juvenile crabs. A new type of accordion-shaped trap with an escape vent(L×W=4.3 cm×3.0 cm) was designed and a comparative study between the newly designed and conventional traps was performed in the artifi cial reef area of Zhuwang, Laizhou Bay, China from June to August 2012. The mean catch per unit effort(CPUE) of undersized crabs was signifi cantly lower in the vented traps than in the conventional traps(paired t-test, n =30, P <0.001), while the CPUE of marketable crabs was signifi cantly higher in the vented traps(paired t-test, n =30, P <0.001). The mean size of crabs(carapace length) caught in the vented traps was signifi cantly larger than in conventional traps(paired t-test, n =29, P <0.001). The ratio of undersized crabs was 35.05%±2.57% in conventional traps and 12.53%±0.69% in vented traps(signifi cantly lower, paired t-test, n =29, P <0.001). Therefore, a 4.3 cm×3.0 cm escape vent was considered appropriate for C. japonica fi shing in the artifi cial reef area. This fi nding will assist the development of more sustainable and effi cient crab fi shing methods using accordion-shaped traps.

Attaching Organism Community Characteristics of Different Surface Treatments on Artificial Reef Tem-plates Inshore of Yuanzhou Island

In order to understand the biological community characteristics of different surface treatments of ＇artificial reef templates ,which had been placed on the offshore, Yuanzhou island, Daya Bay. Sampling survey was taken in August of 2014. The results showed that 39 species of fouling organisms were collected and iden- tiffed, Ostrea nigromarginata has attached the absolute position of the dominant species ; Through the concrete block surface treatment has a better biofouling effect, and red brick, granite plates and no-surface-treated concrete template attached biomass and abundance of organisms were very low ; Biomass and abundance indices and ecological indices do not show a certain degree of regularity.

Evaluation on Fishery Resources in Daxingshan Artificial Reef Area of Huidong County

In order to evaluate placement of artificial reefs in Huidong County and observe biological aggregating effect of fishery resources,background investigation and follow-up investigation were carried out for trawl fishing and gill-net fishing in Daxingshan artificial reef area.The biological resource density index(D),Margalef species richness index(R),Shannon-Winener diversity index(H'),and Pileou evenness index(J')were used to study diversity of water biological population and resource density.Trawl fishing investigation indicated that after placement of reefs,there was significant increase in quantity of species of nekton,total resource density,species richness index,and diversity index in reef area,which were 1.321,2.07,1.012 and 1.084 times the value before placement of reefs respectively.Gill-net fishing investigation indicated that after placement of reefs,the quantity of species of nekton,total resource density,species richness index,and diversity index in reef area were 2.571,7.976,2.399 and 2.667 times the value before placement of reefs respectively.After reef placement,fishes and crabs become dominant population.It showed that after reef placement,attraction effect of fishes is significant,community structure is obviously optimized,and water environment in reef area is significantly improved.Thus,it proved that the multiplication system through artificial reefs has been basically established in Daxingshan reef area of Huidong County.